Performance of low-frequency power of the maximal amplitude of the first derivative of arterial pressure waveform as a cardiac sympathetic activity index

We assessed the time-frequency spectra of the maximal amplitude of arterial pulse first derivative (dP/dt
_max
) series during four maneuvers provoking different sympathetic activity levels, and examined the relations between dP/dt
_max
spectral measures and those of heart rate, systolic pressure (SP), and respiratory variabilities. Thirty healthy subjects performed 5-min maneuvers: lying, controlled breathing, standing (S) and exercise (E). Time-frequency spectra of RR intervals (RR), SP, dP/dt
_max
and respiration (Res) time series were estimated to compute their low-frequency powers (LF
_SP
, LFdP/dt
_max
), high-frequency powers (HF
_RR
, HFdP/dt
_max
, HF
_Res
), and HFdP/dt
_max
-HF
_Res
time-frequency coherence. While LF
_SP
and LFdP/dt
_max
increased in S and E, HF
_RR
and RR level decreased. Correlations of HF
_RR
and RR level with LFdP/dt
_max
were very strong and greater than with LF
_SP
. HFdP/dt
_max
was maximal in E and showed significant coherences with HF
_Res
. LFdP/dt
_max
and LF
_SP
correctly indicate the increasing levels of sympathetic activation in S and E. Thus, LFdP/dt
_max
power can be considered a suitable noninvasive cardiac sympathetic activity-contractility index, complementary to LF
_SP
, which is associated to vasomotor sympathetic activity. HFdP/dt
_max
power is originated by a mechanical respiratory effect.